Brazos Heelsplitter (Potamilus streckersoni)
Thought to be an odd range extension of the common freshwater mussel Pink Papershell
(Potamilus ohiensis) from the Mississippi basin, a 2019 study revealed the
Brazos Heelsplitter was a unique species found only in the Brazos: an endemic. The
shell material is usually thinner, and yellowish green in younger specimens, to brown
and almost purple in larger older individuals. The inside surface is often an iridescent
pink to purple depending on age.
Protection Status
The Brazos Heelsplitter is a state-listed threatened species. The Brazos River Authority’s
Environmental Services Department regularly monitors different fish and wildlife species,
including freshwater mussels, as a way of tracking the health of the Brazos River basin
ecosystem.
Importance
Freshwater mussels are an indicator of a healthy aquatic system. They are filter feeders
and thus contribute to water clarity and quality by removing plankton and pollutants from
the water.
The sudden disappearance of mussels in an area not recently subject to prolonged drought
often indicates water pollution problems.
Historically, freshwater mussels were collected commercially for food, pearls and button
making. Commercial harvesting is now regulated by the Texas Parks and Wildlife Department
and requires a license and annual reporting to the department.
Habitat
Originally ranging from the lower Brazos up through the Clear Fork, more recent surveys find
them predominantly in the mainstem of the Brazos River downstream of Waco, and venturing near
the confluences of the Little River, Navasota River, and Yegua Creek. The Brazos Heelsplitter
is commonly found in soft substrates like sand, silt and mud near banks, backwaters, and pools.
Life Cycle
Little is known regarding the life history of the Brazos Heelsplitter. They are presumed
to have a similar reproductive cycle to other Potamilus species, which are
long-term brooders that parasitize solely on Freshwater Drum Aplodinotus grunniens
to complete their life cycle.
Like all freshwater mussels, the Brazos Heelsplitter is relatively inactive and capable of
moving only small distances. Their primary mode of moving or colonizing new areas is accomplished
by the movement of the fish hosts or by high flow events that scour adult mussels from their
current location and move them downstream.
The breeding season of the Brazos Heelsplitter has not been definitively documented. Still,
it is presumed to follow the primary breeding season of other freshwater mussels, which most
frequently occurs from February to June.
Ongoing Research
A significant amount of research is done on freshwater mussels. Agencies across the state are
researching them, including the U.S. Fish and Wildlife Service, the Texas Comptroller of Public
Accounts, the TPWD, and the Brazos River Authority.
Several universities also are researching freshwater mussels, including Texas A&M University,
Texas State University, Baylor University, the University of Texas at Tyler, and Auburn
University. These studies include surveys to identify new populations, genetic investigations,
and tolerance studies.
The TPWD also maintains the Texas Mussel Watch Program,
where members of the public can submit their observations of mussels to help gain
a better understanding of the distribution and status of mussels.
In addition to regulating commercial harvesting of mussels, the TPWD also regulates the
taking of mussels by individuals by requiring a fishing license and freshwater fishing
endorsement.
In August 2020, the Brazos River Authority submitted a Candidate Conservation Agreement
with Assurances to the U.S. Fish and Wildlife Service for consideration, in which the
BRA commits to performing voluntary conservation activities aimed at reducing threats
to the Texas fawnsfoot, and Balcones Spike. Such actions are therefore beneficial to
Brazos Heelsplitter occupying much of the same range in the Brazos basin. This agreement
was executed in mid 2021.
For more information, go to:
Citations:
- Smith, Chase & Johnson, Nathan & Inoue, Kentaro & Doyle, Robert & Randklev, Charles. (2019). Integrative taxonomy reveals a new species of freshwater mussel, Potamilus streckersoni sp. nov. (Bivalvia: Unionidae): implications for conservation and management. Systematics and Biodiversity.
- Barnhart, M.C., W.R. Haag, and R.N. Williams. 2008. Adaptations to host infection and larval parasitism Unionoida. Journal of the North American Benthological Society. 27:370-394.
- Bonner, T.H., E.L. Oborny, B.M. Littrell, J.A. Stoeckel, B.S. Helms, K.G. Ostrand, P.L. Duncan, and J. Conway. 2018. Multiple freshwater mussel species of the Brazos River, Colorado River, and Guadalupe River basins. Final Report to Texas Comptroller of Public Accounts.
- Howells, R.G., 2014. Field Guide to Texas Freshwater Mussels. BioStudies, Kerrville, TX.
Read more about the other threatened species of interest here.